Selective circuit for multiplex transmission



May 22, 1923.

H. A. AFFEL SELECTIVE CIRCUIT FOR MULTIPLEX TRANSMISSION Filed Sept. 24,1919 INVENTOR.

Patented May 22, T1923.

M A. AFFEL, OE BROQKLYN, NEW YQRK, ASSIGNOB TO EC TELEPHONE TELEGRAPHCOMPANY, A CQRPOBATION OF N YORK.

' instant rray SELECTIVE CIRCUIT FOR MULTIPLE TRANSMISSION.

Application filed September 24, 1919. Serial Ito. 325,841.

To all whom it may concern: 1

Be it known that I, HERMAN residing at Brooklyn in the county of Kingsand State of New York, have invented certain Improvements in SelectiveCircuits for Multiplex Transmission, of which the following is aspecification.

This invention relates to signaling systems and more particularly tosystems in which a plurality of signals are simultaneously transmittedover the same conductor.

One of the principal features of the invention resides in the provisionof an arrangement whereby a plurality of signals may be transmitted overa grounded conductor such as a submarine cable.

Still another feature of the invention relates to the provision ofarrangements whereby a channel for the transmission of ordinary voicecurrents and a number of channels for the transmission of telegraphsignals or additional telephone channels by the use of carrier currentsmaybe simultaneously superposed upon a grounded conductor such as asubmarine cable.

The above features, together with other features of the invention morefully hereinafter appearing, are realized by superposing upon theordinary voice currents transmitted over a submarine cable, a pluralityof carrier currents having frequencies in some instances above and insome instances below the voice range, together with ordinary Morsecurrents, the several channels beingseparated by means of frequencyselectivity.

The invention may now be more fully understood by reference to thefollowing description when read in connection with the accompangdrawing. Referring to the drawing, t? r designates'a transmission C11-cuit such as a submarine cable, which forms one'conductor of atransmission circuit employing a grounded return. An artificial line ornet work MN is provided for balancing the cable MN and a plurality ofparallel signaling paths, 1-1, 2-2, 3-3, 4-4 and 5-5 are provided forinterconnecting the cable and artificial line. Morse transmitting aparatus T and Morse receiving apparatus 1 is associated with the junctionpoints of the paths 1 and 1", the polar receiving relay having itswindings so arranged that one-half 18 included in each of the paths 1and 1, while transmitted our- A. Arena,

rents from the transmitter T are applied to the midpoints of thewindings 11. An alternating current telegraphic transmitting apparatus Tis applied to the midpoints of the windings of a balanced transformer12, connected in the path 2-2, while an amplifying and detectingarrangement 1), and

a receiver R, is inductively associated with the path through saidtransfdrmer. Atelephone transmitter T is arranged to apply telephoniccurrents to the midpoint of the windings of a transformer 13 in the path3-3, while a tele hone amplifier A, and telephone receiver 3 areinductively associated with said path through said transformer 13. In asimilar manner carrier transmitting arrangements T and T are connectedto the midpoints of the windings of transformers 14 and 15 included inthe paths 4-4 and 5-5. Detecting and amplitying arrangements D, and Dhavin receiving devices R, and R, associated t erewith are inductivelycoupled to said paths through the transformers 14 and 15 respectively.

It will be observed that the arrangement above described is such thatall of the transmitting devices are conjugate with respect to all of thereceivi devices' and viceversa, so that there wil be substantially nointerference between oppositely directed transmissions, regardless ofthe frequencies. In order to provide for frequency. separation betweentransmission in the same direction, filters or selectin circuits F FF,,, F, and F are provide in the paths 1, 2,

3, Land 5, respectively. These filters may be of any well-knowncharacter, but are preferably band filters of the type disclosed in theU. S. Patents to George A. Campbell,

Nos. 1,227,113 and 1,227 ,114, dated May 22, 1917.

illustrated, is designed to transmit a range of frequencies extendingfrom zero to 100 cycles, this range being suiiicient to take The filterFmay be a low filter and, as

In order to balance the filters F to F inelusive, balancing networksshould be provided in the corresponding halvesof the signalin pathsdesignated 1' to 5' inclusivc. iese balancing arrangements may compriseany suitable form of networkwhose electrical characteristics simulatethose of the filter to be balanced. As illustrated, however, duplicatefilters F F F F andF, are provided for balancing the selective filtersF, F, inclusive. The filters F to B, should each transmit the same bandor frequencies as the filter which it is intended to balance. lit willbe understood, of course, that the various frequencies above referred toare given merely for purposes of illustration and that in actualpractice other frequencies than those indicated may be used.

It will be seen that by means of the arrangements above disclosed it ispossible to utilize the full frequency capacity of an expensiveconductor such as a submarine cable, so that in addition to the ordinaryMorse signals ordinarily transmitted a telephone channel as well as anumber of additional carrier telephone or telegraph channels areprovided. 0

It will'be obvious that the general principles herein disclosed may beembodied in many otherorganizations widely different from thoseillustrated, without departing from the spirit of the invention asdefined in the following claims.

What is claimed is:

1. In a multiplex system, a transmission circuit, balancing meanstherefor, a plurality of signaling paths connected in multiple betweensaid transmission circuit and balancing means, said balancing meanssimulating the impedance of the transmission circuit at the frequenciestransmitted over each of said paths, means whereby telephone currents ofvoice frequencies may be transmitted from one of said paths. over saidtransmission circuit, means whereby signal ing currents havingfrequencies below the lower voice limit may be transmitted over certainother of said paths, means whereby signaling or carrier currents havingfrequencies above the upper voice limit may be transmitted over saidtransmimion circuit through still other of said paths, and means tosubstantially prevent in each of said paths the transmission offrequencies from the other paths.

2. In a multiplex signaling system, a

transmission circuit, balancing means therefor, a plurality of signalingpaths connected in multiple between said transmission circuit and saidbalancing means, said balancing'meanssimulating'the impedance of thetransmission circuit at the frequencies transmitted'ovcr each of saidpaths, means associated with one of said paths for transmitting andreceiving Morsecurrents, means associated with another of said paths fortransmitting and receiving alternating carrier currents whose frequencyis less'than that of the lowest frequency employed in ordinarytelephonic transmission, means associated with a. third of saidpaths fortransmitting and receiving ordinary telein multiple between saidtransmission cir cuit and balancing means, said balancing meanssimulating the impedance of the transmission circuit at the ire uenciestransmitted over each of said pat is, telephonic transmitting andreceiving apparatus associated with one of said paths and telegraphictransmitting and receiving apparatus associated with the remainingpaths, certain of said apparatus being arranged to transmit and receivefrequencies above the upper voice limit, other of said apparatus beingarranged to transmit and receive frequencies below the lower voicelimit, and means to substantially prevent in each of said paths thetransmission of frequencies from the other paths.

4. In a multiplex signaling system, a transmission circuit, comprising agrounded cable conductor, an artificial line or network, a plurality ofsignaling paths connected in multiple between said transmission circuitand artificial line, said artificial line simulatingthe impedance of thetaransmission circuit at the frequencies transmitted over eanh of saidpaths, and selective means in said paths for providing frequencydiscrimination between alternating currents transmitted overthe paths.

5. In a multiplex signaling system, a transmission circuit comprisingagrounded cable conductor, an artificial line or network, a plurality ofsignaling paths connected in multiple between said transmisessee? sioncircuit and artificial line, said artificial line simulating theimpedance of the transmission circuit at the frequencies transmit-' tedover each of said paths, selective means in said paths for providingfrequency dis-i crimination between the paths, the selective meansassociated with one of the paths permitting the transmission of ordinaryvoice currents, the selective means associated with other of said pathspermitting the transmission only of signaling frequencies below thelower limit of voice transmission and theselective means associated withstill other ofsaid paths permitting the transmission only of signalingor carrier frequencies above the upper llfllllilllgLVOlCQ frequency.

6. In a multiplex transmission system a transmission circuit comprisinga grounded cable conductor, an artificial line or network, a pluralityof signaling paths connected in multiple between said transmissioncircuit and artificial line, said artificial line eiated with stillother of said paths, said carrier current apparatus employingfrequencies above the upper limiting telephonic frequency, and means tosubstantially prevent in each of said paths the transmission offrequencies from the other paths.

In testimony whereof, I have si ed my name to this specification this23r day of September 1919.

HERMAN A. AFFEL.

